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∫xx−x2−1 dx\displaystyle\int \dfrac{x}{x-\sqrt{x^2-1}}\,dx is equal to :

Solution

✅ Correct Option: 4

Rationalise by multiplying numerator and denominator by x+x2−1x+\sqrt{x^2-1}; the denominator becomes x2−(x2−1)=1x^2-(x^2-1) = 1.

The integral reduces to ∫x(x+x2−1)dx=∫x2dx+∫xx2−1 dx\int x\left(x+\sqrt{x^2-1}\right)dx = \int x^2 dx + \int x\sqrt{x^2-1}\,dx.

This gives x33+(x2−1)3/23+C\dfrac{x^3}{3}+\dfrac{(x^2-1)^{3/2}}{3}+C.

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